The present invention generally relates to a semiconductor apparatus, and more particularly, to a semiconductor apparatus with a semiconductor chip of larger construction power density being mounted on the semiconductor apparatus, and a method for manufacturing thereof.
Generally, consumption power per semiconductor chip increases steadily as semiconductor art presently develops. Especially, a demand for transistors for power amplification use in a microwave band increases, and a low cost mounting art capable of high efficiency of radiation which can be used for the semiconductor apparatus has an urgent necessity for being established. The following method is proposed broadly as a mounting method capable of being used with the semiconductor apparatus.
a) PHS (Plated Heat Sink) N. L. Wang et al., IEEE Trans. on "Microwave Theory and Technol.", vol. 38, No. 10, pp. 1381-1389
A means for releasing heating of a splicing portion of a semiconductor chip onto the basic plate reverse face side of the basic plate is adopted in the above described document. Namely, (1) a semiconductor basic plate is cut thin, and (2) a via hole extending onto the basic plate surface side from the basic plate reverse face side is provided immediately under an electrode drawn out onto the periphery of the semiconductor chip from the splicing portion, with a metallic material which is good in thermal conductivity being buried in the via hole.
b) Flip Chip
1) A method for forming a bump electrode to be mounted on a flip chip after the basic plate is made in a thin layer, and, radiating by way of a case cap or the like with the use of, for example, heating solder or the like from the reverse face of an element basic plate is well known as disclosed in Japanese Patent Application Publication No. Sho 62-249429 (unexamined).
Generally an insulating material such as a ceramic and the like is used as a connecting member for externally transmitting the heat from the element basic plate. That is why the bump is required to function as a plurality of electrodes which are different in electric role and a wiring pattern for connecting the outside with them is required to be supported on the same plane face without being short-circuited as all the top faces of the semiconductor chip mounted by the inversion are covered with the connecting member.
Heat transmitted to the reverse face of the semiconductor chip is radiated partially into the open air by way of a package cap, and the majority of the heat is transmitted to the lower portion by way of the above described connecting member, and is radiated externally. Most of the thermal resistance is transmitted to the lower portion by way of the above described connecting member and is prescribed with ease of external radiation. A member to be thermally connected with the reverse face of the chip serves for a package cap so that the member is made larger than the chip so as to retain the positional alignment roof. Therefore, the distance between the chip and the position where the member is spliced with the above described connection member is large.
2) A method of assembling a metallic heat sink and an insulating basic plate provided adjacently to the metallic heat sink with -the height thereof being arranged, and further, mounting a flip chip is well known as disclosed by Y. Mitsui, et al., IEEE Trans. on "Microwave Theory and Technol.", vol. MTT-29, No. 4, pp. 304-309.
The above described conventional method a) has disadvantages as follows.
i) As the basic plate is cut in, and further, the via hole is opened, a crack notch is caused in a wafer so as to reduce the yield. PA1 ii) The via hole is subject to restriction in the working precision so as to be separated by at least 5 .mu.m or more from the splicing portion, i.e., heating location. Therefore, it is difficult to effectively reduce the thermal resistance. PA1 iii) In the microwave band, an outgoing line from the splicing portion has non-negligible inductance. The outgoing line functions as feedback inductance and has loss. PA1 ii) As the distance between the chip and the position where the member to be thermally connected with the reverse face of the chip is connected with the connecting member is larger, it is difficult to sharply reduce the thermal resistance caused by this distance. PA1 iii) A wiring pattern for electrically connecting the bumps to each other or the outside is required to be provided on the side of the connecting member, thus causing higher cost. PA1 iv) As the working precision is worse when the wiring pattern is provided chiefly by thick film printing to the ceramic on-the side of the connecting member, it is difficult to refine the pattern. PA1 v) As a wiring pattern exists on the connecting member, and the high positional alignment accuracy with respect to wiring pattern is required, the cost becomes higher. PA1 i) It is very difficult in art accompanied by differences etc. in thermal expansion coefficient to assemble, with the height thereof being aligned in order to provide completely the bump connection, a metallic heat sink, mainly, non-oxygen-copper used as the superior thermal conductivity and an insulating basic plate, mainly, ceramics, adjacent to the bump connection, thus resulting in higher cost. PA1 ii) As a specific bump has to be bonded on a specific position in the mounting operation of the flip chip, the yield is lowered, thus resulting in higher cost. PA1 a) The normal positioning of the semiconductor chip makes it possible to use the electrode connecting means having a lower price, and higher in reliability as will be described later. PA1 b) Heating from a device made on the semiconductor chip surface is radiated by way of the bump.fwdarw. the connecting member.fwdarw. the connecting face. Accordingly, the connecting face is brought into approximate proximity with respect to the semiconductor chip and brings the contraction of the thermal route and the reduction of the thermal resistance. PA1 c) To bring the connecting face into approximate conformity with a plane for connecting the bump to the highest portion considerably simplifies the working of the connecting member for connecting them and the positional alignment. PA1 d) The connecting member constitutes one portion of the radiating route described in the paragraph a) above. Also, the connecting member may be used as an electrode. PA1 e) When the semiconductor chip is mounted, the end portion of the connecting face becomes a "guide", and the positional alignment accuracy is improved if a special means is not provided. PA1 a) A portion not covered on the immediate top of the chip is the easiest portion for drawing out the electrode. Accordingly, the electrode connecting means, which is lower in price and higher in reliability is drawn out by, for example, a method of wire bond or the like. PA1 b) By electrode connecting means which does not rely upon the connecting member, the bump does not necessarily require functions as a plurality of electrodes different from the electric role. Accordingly, the connecting member is not required to be supported on the same plane without short-circuiting the wiring pattern for connecting them with the outside. Thus, the material quality of the connecting member can be freely selected. Also, the wiring pattern and so on are not required to be built in by the working operation on the connecting member itself.
The above described convention method b) 1) has disadvantages as follows. p1 i) As the connecting member has no choice but to become an insulating material, the thermal conductivity is inferior. It is difficult to considerably reduce the thermal resistance caused due to the connecting member.
The above described conventional method b) 2) has disadvantages as follows.
Therefore, it is difficult to put it to practical use due to such problem points as mentioned above.